1. Field of the Invention
The present invention relates to a display control apparatus and a display control method of controlling the display of a display device such as a dot matrix display device. More particularly, the invention relates to a display control apparatus and a display control method capable of displaying an input signal on a display device even if the input signal has a different resolution from that of the display device.
2. Related Background Art
Raster scan type CRT display devices are widely used with host computers such as personal computers and work stations. Flat panel display devices such as liquid crystal panel display devices and plasma display devices have recently drawn much attention from the viewpoint of space reduction, energy savings and ergonomics (methodology of configuring a system to suit human characteristics by studying optimum working environments).
Between a host computer and a CRT display device, a so-called video signal or analog video data, vertical and horizontal sync signals are transferred or an aggregation thereof (composite signal) is transferred. There are many specifications which define video signals, and some apparatuses, particularly personal computers provide a plurality of resolutions.
For example, some IBM compatible personal computers (PCs) can provide resolutions of 320×200 dots, 640×400 dots, 720×400 dots, 640×350 dots, 640×480 dots, 800×600 dots, 1024×768 dots, 1280×1024 dots and the like.
On the side of CRT display devices, there are so-called multi-sync CRT display devices which measure sync signals of the video signal and determine drive periods of a scan line and its swing width to match the measured sync signals.
Some CRT display devices store in advance measured video signals or sync signals of several types of host computers in a memory as display parameters. If a CRT display device can identify a host computer when the sync signals are measured, it uses the display parameters stored in the memory so that a more precise display of such as a display position can be produced.
The above-conventional display devices are, however, associated with the following problems. Dot matrix display devices such as liquid crystal display devices and plasma display devices adopt a display control method suitable for digital signals. Therefore, after an input analog image signal is A/D converted, it is displayed. In this case, generally, one pixel of a video signal is sampled and displayed in correspondence with one pixel of a display panel, because of the current technical standards of dot matrix display devices.
If a video signal with a low resolution is to be displayed on a dot matrix display device having a high resolution, it becomes necessary to perform a video signal expansion process through interpolation. In addition to this problem, another problem is that a real time display of an image with plentiful motions on a display device having a low refresh rate is impossible unless the image data has a resolution lower than the vertical resolution of the display device.